Infrared sensor apparatus

Abstract: An infrared sensor apparatus of the present invention has an infrared array element having infrared detection portions arranged at a plurality of positions in a two-dimensional array, and a plurality of infrared lenses arranged such that infrared images from a detection area divided into a plurality of portions are formed on the corresponding infrared detection portions without any superposition. These infrared lenses are a plurality of cylindrical lenses or Fresnel lenses.

Description: BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention relates to an infrared sensor apparatus for detecting an infrared heat source such as a human body. 2. DESCRIPTION OF THE RELATED ART Fig. 1 is a view showing a conventional infrared sensor apparatus. In this infrared sensor apparatus, one Fresnel lens 2 as an infrared lens is arranged for one infrared sensor 1 on the incident side of the sensor 1. This Fresnel lens 2 defines, e.g., a plurality of infrared detection areas A to D. However, in this infrared sensor apparatus, for example, when an infrared heat source such as a human body enters the infrared detection areas A to D, the Fresnel lens 2 condenses infrared radiation from the plurality of areas, thereby detecting the infrared heat source by one fixted infrared sensor 1. In this case, only the presence/ absence of an infrared heat source or movement thereof is detected. A plurality of pieces of information such as the position, the moving direction, and the moving speed of the infrared heat source can hardly be detected in detail. To detect information from an infrared heat source in detail, a method is proposed, in which the fixed infrared sensor 1 and the Fresnel lens are mechanically moved to form the plurality of detection areas A to D. In another infrared sensor apparatus, as shown in Fig. 2, a plurality of infrared sensors 1A to 1D are disposed. The condensing portions of the Fresnel lens 2 are disposed in correspondence with the infrared sensors 1A to 1D, thereby individually detecting infrared radiation from the detection areas A to D. In the method of mechanically moving one infrared sensor 1, however, a moving unit, movement control unit and the like are required, resulting in a bulky and complicated apparatus. When the plurality of infrared sensors 1A to 1D are used, as in Fig. 2, the condensing portions of the Fresnel lens 2 must correspond to the infrared detection areas A to D. In this case, since a large lens is used, highly precise manufacturing of the lens becomes very difficult, and images may be blurred in some regions of the lens. Additionally, the apparatus becomes bulky and expensive. US Patent 4 321 594 discloses an infrared sensor apparatus in which a plurality of detectors, disposed in a matrix-like arrangement, are employed. Each detector has a corresponding Fresnel lens which condenses infrared radiation onto the detector. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a compact and inexpensive infrared sensor apparatus capable ofaccurately detecting a plurality of pieces of information and is easy to assemble without requiring the highly precise manufacture of an infrared lens. The invention is defined by the appended claims. In order to achieve the above object, according to the first aspect of the present invention, there is provided an infrared sensor apparatus comprising an infrared array element having infrared detection portions arranged at a plurality of positions in a two-dimensional array, and a plurality of infrared lenses arranged on an infrared incident side of the infrared array element such that infrared images from a detection area divided into a plurality of areas are individually formed on the corresponding infrared detection portions without any superposition. According to the second aspect of the present invention, there is provided an infrared sensor apparatus wherein the plurality of infrared lenses of the first aspect are a plurality of cylindrical lenses, and one of the cylindrical lenses is arranged in correspondence with each array of the detection portions in a column or row direction of the infrared array element. According to the third aspect of the present invention, there is provided an infrared sensor apparatus wherein the plurality of infrared lenses of the first aspect are a plurality of Fresnel lenses, and one of the Fresnel lenses is arranged in correspondence with each array block including the detection portions whose number is the same in column and row directions of the infrared array element. According to the present invention, a plurality of infrared lenses are disposed in correspondence with a plurality of detection portions of a two-dimensional infrared array element such that infrared images from infrared detection areas are formed on the corresponding infrared detection portions without any superposition. Therefore, infrared radiation incident from an infrared heat source such as a human body is condensed by the infrared lenses corresponding to the infrared detection areas and focused on the corresponding detection portions. The infrared detection portions individually output signals. By analyzing these output signals, a plurality of pieces of information such as the position, the size, the moving direction, and the moving speed of the infrared heat source can be accurately detected. In addition, one two-dimensional infrared array element is used as the infrared sensor, and a plurality of infrared lenses are used. With this simple arrangement, the infrared sensor requires neither a driving unit nor a driving control unit, so that a compact and inexpensive infrared sensor apparatus can be manufactured by easy assembling. Furthermore, as is well known, a cylindrical lens focuses incident infrared radiation without blurring and variations. With the arrangement in which the cylindrical lens is used as the infrared lens, the infrared radiation is condensed without variations, and an image is formed without blurring. Therefore, highly accurate detection of information can be performed. The above and many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the following detailed description and accompanying drawings in which preferred structural embodiments incorporating the principles of the present invention are shown by way of illustrative example. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view for explaining a conventional infrared sensor apparatus; Fig. 2 is a view for explaining another conventional infrared sensor apparatus; Figs. 3A and 3B are explanatory views of an infrared sensor apparatus according to the first embodiment of the present invention; Fig. 4 is an explanatory view of an infrared array element in the first embodiment of the present invention; Figs. 5A to 5D are explanatory views of output signals from the infrared sensor in the first embodiment; and Fig. 6 is an explanatory view of an infrared sensor apparatus according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Figs. 3A and 3B are views showing an infrared sensor apparatus of the first embodiment. This infrared sensor apparatus has, as shown in Fig. 4, an infrared array element 5 as an infrared sensor, and a plurality of cylindrical lenses 6A to 6D as infrared lenses. The infrared array element 5 includes a plurality of infrared pixels 3 comprising, e.g., pyroelectric electrodes arranged in a two-dimensional array (a plurality of pixels are arrayed in both the column and row directions). The cylindrical lenses 6A to 6D consist of, e.g., high-density polyethylene or the like. The cylindrical lenses 6A to 6D are arranged on the infrared incident side of the infrared array element 5 to focus infrared images from divided detection areas a to d on the corresponding infrared pixels 3 of the infrared array element 5 without any superposition. Each of the cylindrical lenses 6A to 6D corresponds to one array of pixels 3 in the row direction of the infrared array element 5. As shown in Fig. 4, the infrared array element 5 is divided into 16 pixels 3. The four arrays in the row direction correspond to the infrared detection areas a to d . The pixels of pixel numbers 1 to 4 detect infrared radiation from only the infrared detection area a , and the pixels of pixel numbers 5 to 8 detect infrared radiation from the area b . Similarly, the pixels of pixel numbers 9 to 12 detect infrared radiation from the area c , and the pixels of pixel numbers 13 to 16 detect infrared radiation from the area d . As described above, detection signals detected by these pixels are individually extracted and amplified by an amplifier (not shown). As shown in Fig. 3B, a floor 4 where an infrared heat source such as a human body enters is divided into 4 x 4 portions in the column and row directions to form 16 areas for descriptive convenience. Areas in the column direction are defined as W, X, Y, and Z, and areas in the row direction are defined as I, II, III, and IV. Figs. 5A to 5D are graphs showing signal waveforms from the infrared sensor of the first embodiment. Numbers along the ordinates represent the pixel numbers of the pixels of the infrared array element 5. An output voltage waveform for each pixel number is shown. Time is plotted along the abscissa. An example of the infrared detection of the first embodiment will be described below, If an adult as an infrared heat source enters area W-III of the floor 4, as shown in Fig. 3B, most infrared radiation from the infrared heat source is condensed by the lens 6D corresponding to the infrared detection area d , as shown in Fig. 3A. As shown in Fig. 5A, a signal having a large waveform is output from the pixel of pixel number 15 corresponding to the entrance position of the infrared heat source. The head portion is in the infrared detection area c , so the infrared radiation is condensed by the lens 6C corresponding to the infrared detection area c . The pixel of pixel number 11 corresponding to the position of the infrared heat source outputs a signal having a midsize waveform, as shown in Fig. 5A. The distal end of the head slightly enters the area b . The infrared radiation is condensed by the lens 6B corresponding to the area b , and the pixel of pixel number 7 outputs a signal having a small waveform. Similarly, if an adult stands in area Y-IV of the floor 4, the infrared radiation is condensed by the lenses 6C, 6B, and 6A corresponding to the infrared detection areas c , b , and a . As shown in Fig. 5B, the pixels of pixel numbers 12, 8, and 4 output signal waveforms each having a corresponding size. Similarly, if a child stands in area X-I, a signal waveform as shown in Fig. 5C is output. If the child stands in area Z-II, a signal waveform as shown in Fig. 5D is output. These output voltages (output waveforms) from the pixels are analyzed, thereby obtaining a plurality of pieces of information such as the position, the size, the moving direction, and the moving speed of the infrared heat source. According to the first embodiment, the cylindrical lenses 6A to 6D are arranged such that infrared images are formed on the arrays of pixels of the infrared array element without any superposition. For this reason, the infrared radiation is condensed by the cylindrical lenses corresponding to the infrared detection areas and focused on the corresponding pixels. Therefore, a plurality of pieces of information such as the position, the size, the moving direction, and the moving speed of the infrared heat source can be accurately detected. In addition, as is well known, a cylindrical lens focuses incident infrared radiation without blurring and variations. In this embodiment, the cylindrical lenses 6A to 6D as infrared lenses are arranged in correspondence with the arrays of pixels of the infrared array element 5. Therefore, the infrared radiation is condensed without variations, and the image on each pixel is not blurred. Furthermore, one infrared array element 5 is used as the infrared sensor, and the cylindrical lenses 6A to 6D corresponding to the number of arrays are used as the infrared lenses. With this simple arrangement, unlike the conventional infrared sensor, neither a driving unit nor a driving control unit are required. Therefore, a compact and inexpensive infrared sensor apparatus can be manufactured by easy assembling. Fig. 6 is a view showing an infrared sensor apparatus of the second embodiment. In this infrared sensor apparatus, as in the first embodiment, a two-dimensional infrared array element 5 is used as an infrared sensor. In this embodiment, a plurality of Fresnel lenses are used as infrared lenses. Each Fresnel lens is arranged in correspondence with pixels whose number is the same in the column and row directions, i.e., 2 x 2 = 4 pixels of the infrared array element 5. That is, in this embodiment, four Fresnel lenses 7A to 7D are arranged in correspondence with array blocks of pixel numbers 1, 2, 5, and 6, pixel numbers 3, 4, 7, and 8, pixel numbers 9, 10, 13, and 14, and pixel numbers 11, 12, 15, and 16. A floor 4 where an infrared heat source such as a human body enters is conveniently divided into 4 x 4 portions in the column and row directions to form 16 areas. Infrared radiation from areas 1, 2, 5, and 6 of the divided floor is focused by the Fresnel lens 7A on the pixels of pixel numbers 1, 2, 5, and 6. The infrared radiation from floor areas 9, 10, 13, and 14 is focused by the Fresnel lens 7B on the pixels of pixel numbers 9, 10, 13, and 14. The infrared radiation from floor areas 3, 4, 7, and 8 is focused by the Fresnel lens 7C on the pixels of pixel numbers 3, 4, 7, and 8. The infrared radiation from floor areas 11, 12, 15, and 16 is focused by the Fresnel lens 7D on the pixels of pixel numbers 11, 12, 15, and 16. The infrared radiation from floor area 1 is focused on only the pixel of pixel number 1 which equals to the floor area number. The infrared radiation from floor area 2 is focused on only the pixel of pixel number 2. The infrared radiation from area 5 is focused on only the pixel of pixel number 5. The infrared radiation from area 6 is focused on only the pixel of pixel number 6. As described above, the Fresnel lenses are arranged such that the infrared images from the floor areas are individually formed on the corresponding pixels without any superposition. In the second embodiment, the infrared array element 5 is divided into four blocks, and one Fresnel lens is arranged for each block. For this reason, the infrared radiation from each infrared detection area is condensed by a Fresnel lens corresponding to the detection area and focused on a block of pixels corresponding to the lens, thereby accurately detecting a plurality of pieces of information. One infrared array element 5 is used as the infrared sensor, and the Fresnel lenses 7A to 7D corresponding to the number of blocks of pixels are used. With this arrangement, as in the first embodiment, a compact and inexpensive infrared sensor apparatus can be manufactured by easy assembling. The present invention is not limited to the above embodiments and can be implemented in various forms. For example, the cylindrical lens consists of a high-density polyethylene material. However, the material is not limited to this as far as it is an infrared transmitting material. The infrared array element is divided into 4 x 4 = 16 pixels. However, the infrared array element may be divided into, e.g., 5 x 5 = 25 pixels. The number of pixels is not limited as far as it falls within a range not adversely affecting the manufacture of the infrared sensor apparatus. In the first embodiment, the infrared lenses are designed and arranged such that the focal points of the infrared lenses do not cause superposition of images between the arrays of pixels of the infrared array element. However, for example, a partition plate of a plastic or the like may be provided between the infrared lenses to prevent superposition of images between the arrays. In the first embodiment, the cylindrical lenses 6A to 6D are arranged in correspondence with the arrays of the pixels 3 of the infrared array element 5 in the row direction. However, the cylindrical lenses 6A to 6D may also be arranged in correspondence with the arrays of the pixels 3 of the infrared array element 5 in the column direction. In the first embodiment, one cylindrical lens is arranged in correspondence with one array of the pixels 3 of the infrared array element 5. In the second embodiment, 2 x 2 = 4 pixels of the infrared array element constitute one block. However, for example, the infrared array element may be divided into 6 x 6 = 36 pixels. In this case, 3 x 3 = 9 pixels may constitute one block, and one Fresnel lens may be arranged for one block including 9 pixels. The number of pixels included in one block is not particularly limited. In both the above embodiments, a pyroelectric electrode is used as the pixel of the infrared sensor. However, in place of the pyroelectric electrode, for example, a resistor whose resistance changes in accordance with the amount of infrared radiation may also be used. Alternatively, a thermocouple element may also be used. The material (element) is not particularly limited as far as it can extract the infrared radiation as an electrical signal.

Claims: An infrared sensor apparatus for detecting at least one infrared heat source in three dimensions comprising: a two-dimensional infrared array element (5) having a plurality of infrared detection portions, each of said plurality of infrared detection portions having a plurality of infrared pixels (3); and a plurality of infrared lenses (6A-D, 7A-D) arranged on an infrared incident side of said infrared array element (5) and directed to a detection space, characterised in that: said detection space is divided into the same number of detection areas as said plurality of infrared detection portions, each of said plurality of infrared lenses (6A-D, 7A-D) corresponding to said detection areas and to said plurality of detection portions, respectively, whereby infrared images from said detection areas are formed on said plurality of infrared detection portions. An apparatus according to claim 1, wherein said plurality of infrared lenses comprise a plurality of cylindrical lenses (6A-D), said plurality of infrared pixels (3) are aligned in plural columns or rows, and each of said plurality of detection areas is divided into the same number of area portions as said infrared pixels (3) of each of said plurality of infrared detection portions, whereby infrared images from said area portions are focused onto said plurality of infrared pixels. An apparatus according to claim 1, wherein said plurality of infrared lenses comprise a plurality of Fresnel lenses (7A-D), said plurality of infrared detection portions are aligned in plural columns and rows, said plurality of infrared pixels (3) are aligned in plural rows and columns, whereby infrared images from said detection areas are focused onto said plurality of infrared detection portions, respectively.

Inventors: HORI KENJI, HORI, KENJI
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1994
Main classification: G08B13
IPC codes: G08B13, G01J1, G01V8